1. Field of the Invention
The present invention relates to a manufacturing method for a slotless stator where a stator winding is secured to the inner periphery of a stator core having no slots, and to a rotating electrical machine incorporating the slotless stator.
This application is based on Japanese Patent Application No. 11-240589, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Heretofore as a rotating electrical machine incorporating a slotless stator where a cylindrically shaped stator winding is fitted to the inner periphery of a cylindrically shaped stator core having no slots, there is known the rotating electrical machine disclosed in Japanese Patent No. 2554859.
Moreover, in the same publication there is disclosed a method where a rod shape temporary support member on the outer periphery of which a stator winding has been performed, is inserted from one end opening of a cylindrically shaped stator core. The temporary support member is then withdrawn leaving the stator winding inside the stator core, and the stator winding is affixed to the inner periphery of the stator core by impregnating the winding with resin and then hardening the resin.
However, with this method, since this involves inserting the stator winding from the end opening of the stator core with the stator winding secured to the temporary support body, the outer diameter of the stator winding must be formed smaller than the inner diameter of the stator core.
Consequently, by simply withdrawing the temporary support member and arranging the stator winding inside the stator core, the stator winding is not secured to the inner periphery of the stator core.
Therefore, resin must be impregnated into the stator winding and hardened, to secure the stator winding to the inner periphery of the stator core with adhesive force. Hence the assembly process becomes complicated.
The present invention takes into consideration the above situation, with the object of obviating the need for a special fixation mechanism or adhesive, to thereby simplify the assembly of a slotless stator.
In order to achieve the above object, the present invention adopts the following means.
That is to say, a manufacturing method for a slotless stator according to the present invention is characterized in comprising an assembly step in which a plurality of divided cores which jointly define a cylindrically shaped a stator core having no slots, are assembled into a cylindrical shape so as to contain a cylindrical shape stator winding therebetween, and wherein the winding has an outer diameter larger than an inner diameter of the stator core in a natural or uncompressed condition of the winding.
With this construction, the stator winding is fitted inside the stator core in a condition of being compressed radially inwards.
At this time, since the stator winding functions as a spring pressing the inside of the stator core so as to expand in the normal direction (the radial outward direction), the winding is pressed by the resilient spring force at that time against the inner periphery of the stator core.
Therefore, by this resilient force the stator winding is mechanically secured to the inner periphery of the stator core, and hence a special fixation mechanism or adhesive is not required.
Furthermore, when a current flows in the stator winding, heat is generated so that an outward expanding force acts on the stator winding. Hence at the time of operating, the winding is secured even more stably within the core.
With the manufacturing method for a slotless stator according to the present invention, in the case where a resilient material is inserted between the divided core and the stator winding, the resilient force acting in the normal direction can be further strengthened, and hence the stator winding can be more stably secured within the core.
In particular, in the case where a silicone sheet which contains a filler with good thermal conductivity such as boron nitride, such as used for transistor heat dissipation purposes is used as the resilient material, the heat dissipation is improved and cooling efficiency is also improved.
With the method of constructing a slotless stator according to the present invention as described above, there is no need for an adhesive for securing the stator winding to the inner periphery of the stator core. However, there is the case where the stator winding is immersed in a resin such as varnish in order to electrically insulate between the windings.
In this case, preferably the resin is impregnated, in a condition with the stator winding secured to the inner periphery of the stator core.
With this construction, the situation where the resin which is thickly attached to the outer peripheral side of the stator winding hardens so that elastic restoration of the stator winding is restricted, can be effectively avoided.
That is to say, if the stator winding is fitted to inside the stator core after being impregnated with resin, the resin hardens before fitting, giving the undesirable situation in that fixation utilising the resilient force of the stator winding becomes difficult. With the above construction, this undesirable situation does not arise.
Moreover, the rotating electrical machine according to the present invention, incorporates a slotless stator where inside a cylindrical stator core having not slots there is arranged a cylindrically shaped stator winding having a larger outer diameter than an inner diameter of the stator core, in a resiliently compressed condition, and the stator winding is secured to the inner periphery of the stator core by a resultant resilient force.
Also with this construction, in the above manner, the stator winding inside the stator core functions as a spring, so that the winding is mechanically secured to the inner periphery of the stator core by the resilient spring force.
Hence a special fixation mechanism or adhesive is not required, giving a rotating electrical machine with simple assembly for the slotless stator there of.